Thermometric system for measuring the freezing point



March 9, 1954 w. H. BUSSEY THERMOMETRIC SYSTEM FOR MEASURING THEFREEZING POINT Filed Jan. 31, 1951 Patented Mar. 9, 1954 THERMOMETRICSYSTEM FOR MEASURING THE FREEZING POINT William H. ,Bussey, Rockford,111. Application January 31, 1951, Serial No. 208,828

.7 Claims.

This invention relates .to a thermometric system for measuring thefreezing point of a liquid and .in particular .for measuring thefreezing points of anti-freeze liquids used in automobile radiators andthe like. As ;is well known, a'number of fundamentally differentchemicals are used as anti-freeze liquids in automobile radiators. Thus,one classof such liquids generally comprises ethylene glycol, with orwithout various compounds for preventing foaming and rust. A stilldifferent class .of compounds utilize alcohols ranging irom methyl up tothehigheralcohols with .or without anti-foaming and antirust agents.These various anti-freze liquidsare all sold under .various trade namesand mixing suchi liquids results in confusion anduncertainty as to.their precise efiectiveness in 'coldweather.

Asa rule, freezing point tables for suchliquids based upon specificgravity have been provided. However, these :tables are reliable only ifithe anti-freeze liquids and radiator mixture remain pure. Frequently anautomobile owner Willstart a Winter season with one .typeof antifreezeand mayadddifferent anti-.freezesas the season progresses. In such case,the specific gravity readings lbecome meaningless and the extent ofprotection against freezing becomes uncertain. Evenif the anti-freezeremains pure, nevertheless, the additionof anti-foaming and anti-rustpreventatives by the user, apart from the anti-freeze liquid itself, mayhave the. eiiect of impairing seriouslythe reliability ofspecificgravity readings.

In order to obviate the abovedisadvantages, this invention provides anovel system for determining accurately the freezing pointof the liquidby subjecting. a smallsampleof the liquid to freezingconditions. Thesystemembodying the invention is simpleand effective and operates withsuiiicient rapidity so that it may be used with substantially thesameease as presentday specific gravity meters.

A structure embodying the present invention is characterizedbymechanicalsimplicity, great accuracyof measurement and readydetermination of thefreezing point together-witha limited requirement of the sample to betested. In accordance with this invention, a device is-pro videdwherein'expansion of compressed gas such as carbon dioxideis relied-uponfor effecting the freezing of a sample. The physical construction of adevice embodying the present invention-is such that when the samplebegins to freeze, the expansion of the frozen sample is utilized to showthe operator that the sample is frozen and to read the indicator wheretemperature is shown. By virtue of thesystem embodying'the presentinvention, the .purity .of the sample is assured :together with acomplete absence of air bubbles .WhiQh :may have a tendency to maskithel ansion :of .the mate iial durin i efiz l Means are also provided forquickly .t aWing;th frozen sample after which the samp :may :b discardedand the system :ready gforaneweeycle of-measurement.

In :order that the invention may be fully -understood, it will now beexplained :in o nn ntio with ;the drawings wherein:

Figure 1 is a view ipartlygin ;section;of :an ,apparatus embodying thepresent invention together .with a diagrammatic showing 10f the qo cuitin which such apparatus ;is connected.

Figure 2 is a-viewon 1ine:;2:2zofztheappara us shown in Figure 31.

Referring ,now to 'the :drawings, sleeve J0 i s provided, this .sleevebeing made p eferably O copper or aluminum -galthqugh any other --;rigid metal ,or plastic may :be :used if desired. sleeve 13 has plugs Hand ;l2;at the -;to pand bottom ends respectively. Blues and I52arealsopreferably of .coppenor. ;bI'aSs 0r aluminum hu may be of anyother @material. .sPreferably, however, the sleeve andiplugs are both ofLmateflalhaving low specific-heat andsoodiheat conduct vit P i ctingthroush aplug H and 1:2 :is :tub .415 having iportion, 16 -;disposedwithin chamber 51;! formed by the sleeve and i h' lill -zT l-h ytl'extends ;through plug. {2 and -is. coupled:to and 8 of atti -section Bu-11don tub ene a l indicated bynumeral 1,2,0. JBOurdOn;tube ;20-;has cion 159, this secti n carrying :end 18. i2 section i9 -.te.rminates;-.inp portions! Lcthtrzhi continuingrto .B urdon. section 52:2 lyin adjac nBourdon section 19 and having end portion 23' passing-through bottomplug (t2 and terminating in the :bottom :of chamber :H. .aBWIClOILzU-lhportions l9 and :22; are :elliptical in .--cross -section, due.togbendinqand havea tendencygto straighten out when the pressure witninvthe pipe,goes above atmospheric pressure. ;l t is-understqodthatthe Bourdon tubeis .of -bra-ss, doronze -;or copper $.9 ny other zresilient -.metal;s,uiable ;for the pu pose.

.Gccpemti zwith loop 1130 1 911 1.2! of :the Bourdon tube .par :isele.o.tric :switch :15 (carryin feeler finger :26 .-abutting;a ainst:the :movable end of theBourdon tube. It-is understood that switch 25111s srisidlussecured so. as to tbeffiXedrWith relation to .-s1ee.ve :l0 and :the :Bcurdon tube :is free to .amove the ilooped send he srihtsivit incr ase .in pressure within zthevtube. Fi-nger;z2 6 is part of:a suitable switch mechanism so i that slightmovement of rfinger 2.5 tothe :right .:will serve to operatea switch. Such switches :are

available in the trade, one particular type of switch being sold underthe name microswitch. As a rule such switches may be operated by amovement of finger 26 of the order of a few hundredth of an inch. Otherswitches and switch mechanism may be used. Inasmuch as such switches arewell known, no attempt is made to describe the construction.

Disposed within chamber ll of the sleeve is tube 28 of a metal such ascopper or the like. Insulatingly sealed within tube 28 is resistanceelement 29 of any suitable material, such as nickel, German silver orthe like having a substantial temperature coefficient. Tube 28 and thesealed resistance element 29 are carried within the chamber andcapillary tube 30, carrying insulated wire 3| within it, passes throughplug l2. Tube 28 forms one pole and wire 3| forms the other pole oftemperature-responsive resistor 29. It is preferred to have tube 28 ofcopper or other good heat-conducting material and the resistance elementwithin the tube is so disposed that the entire tube and resistanceelement can quickly adapt itself to the temperature prevailing withinchamber I1.

Plug carries tube 32 of copper or the like, this tube extending throughplug H and terminating at the top of chamber l'i. Plug II also carriessleeve 34 of copper or other suitable metal carrying rod 35 andcapillary tube 38 coiled around the rod within sleeve 34. Capillary tube36 is of fine copper tubing or brass tubing as desired and terminates at39 near end 39 of sleeve 34 at the bottom of chamber Rod 35 extends intosleeve 34 to the bottom thereof and the rod and sleeve are soldered orotherwise attached at the end, the sleeve being sealed as far as chamberI1 is concerned.

Capillary tube 36 terminates in a suitable fitting 4| to which may beattached a tank of compressed gas such as carbon dioxide, it beingunderstood that a suitable valve control is provided. The arrangement ofcapillary and rod within sleeve 34 is such that compressed gas goingdown to the capillary is discharged from the end of the capillary nearthe bottom of the sleeve and escapes into the helical region formedaround rod 35 between the turns of the capillary. The gas is finallyallowed to escape at the free end of sleeve 34, it being understood thatthe length of capillary, the pitch of capillary turn and the relativedimensions of sleeve and rod are so designed as to produce a desiredcooling effect around the outside of the sleeve within chamber I1.

Referring now to the electrical connections, temperature-responsive coil29 forms one arm of abridge. Thus tube 30 is grounded to the instrumentwhile wire 3| has one point 3| of the bridge. Between ground 30 andbridge point 44 is variable resistor 45. Between bridge point 44 andbridge point 46 is resistor 41. Bridge point 45 is connected to oneterminal of resistor 48, the other terminal of this resistor going tofixed contact 50 of one section of a ganged switch. Fixed contact 50cooperates with movable contact this being connected by wire 52 tobridge point 3|. Movable contact 5| is also adapted to cooperate withfixed contact 54 connected to lamp 55 having one terminal grounded.

Bridge point 44 is connected to one terminal of meter or indicatinginstrument 56, the other terminal of this instrument being connected tofixed contact 51 of Bourdon tube switch 25. Fixed contact .5] cooperateswith movable contact 59, this being connected to bridge point 3|.Movable switch contact 59 also cooperates with fixed contact 69, whichcontact is connected by wire 6| to fixed switch contact 62 of the secondsection of the ganged switch. Fixed switch contact 52 cooperates withmovable contact 63 connected through variable resistor 64 to terminal 65of transformer winding 66. Transformer winding 66 has its bottomterminal grounded and has intermediate terminal 61 connected throughrectifier 69 to movable contact 10 of a third section of the gangedswitch. Movable contact 10 cooperates with fixed contact 1| connectedthrough resistor 12 to bridge point 46.

Transformer winding 66 is a secondary of a transformer whose primary T4is adapted to be supplied by conventionalllO volt 60 cycle current. Asis readily apparent, the movable contacts of the three ganged switchsections move as a unit. The left hand position of the movable contactsis used when the device is indicating a freezing temperature while theright hand position of the switches is used when it is desired to thawthe frozen mixture and discard the liquid.

The operation of the system is as follows: Assume that the switchcontacts are in the position shown. A sample of liquid to be tested isforced into tube I5 by a syringe or any other suitable means. The sampleshould be sufliciently large so that any previous liquid remainingwithin the Bourdon tube parts and within chamber I1 is flushed out. Byhaving the volume of chamber rather small and having the Bourdon tubeshort, it is possible to satisfy this requirement without using morethan a small quantity or liquid. It is understood that the apparatuswill be in the position as shown and when liquid is discharged fromdrain pipe 32 in suflicient quantity, the apparatus is ready tofunction, the Bourdon tube and chamber being filled with clean liquidfree of air bubbles. Any air bubbles in the system will be flushed outand tend to rise in drain pipe 32. Assuming that capillary 36 isconnected to a tank of compressed gas, such as carbon dioxide, the valvefor controlling the gas may be opened momentarily and a shot ofcompressed gas given to the capillary. As is well known, the expansionof the compressed gas around the capillary within sleeve 34 and insideof chamber will result in the temperature within the chamber beingreduced. The liquid Within chamber will begin to freeze, this freezinggenerally beginning at the top of the chamber and progressing downwardlywithin the chamber toward plug l2. As the liquid within chamber freezes,it expands and exerts pressure upon the liquid within Bourdon tube part22. This pressure is communicated to the liquid in the Bourdon tube, theliquid within portion l6 of the pipe being frozen and acting to maintainthe liquid within the Bourdon tube under pressure.

With the manually controlled switches in the position shown, rectifiedcurrent from intermediate terminal 91 and ground of the transformerwinding will cause a predetermined difference of potential to existacross bridge points 44 and 3|. The resistance of temperature-responsiveelement 29 will unbalance the bridge as the liquid cools and causesmeter 56 to indicate the temperature, assuming that the meter isproperly calibrated. The bridge arrangement is well known and makes itpossible to indicate accurately the potential difference across bridgepoints 3| and 44 and thus the corresponding tempera-- ture in spite ofvariations in potential applied to the bridge. Variable resistor 45 isprovided for calibrating the bridge.

When the liquid in chamber IT is freezing, switch 25 is operated to movecontact 59 away from 51 to 60.

It is understood that in reading meter 56, the maximum swing of theneedle during freezing should be observed, this indicating the freezingpoint of the liquid. It is possible to obtain temperatures below thefreezing point of the needle, this, in general, being due to excessivequantities of compressed gas being used. However, since a substantialquantity of heat is absorbed by the liquid during the freezing processwithout change of temperature, the operation of switch 25 duringfreezing makes it possible for an accurate reading of the freezing pointto be obtained before the meter is disconnected.

After the temperature of the frozen liquid has been obtained, the manualswitch is thrown to the right. When this occurs, rectified current is nolonger applied to the bridge terminals. Instead, the potential of theentire transformer secondary is applied. The circuit may be traced asfollows: terminal 65 through resistor 64, switch contacts 63 and 62,wire BI, switch contacts 60 and 59 to bridge point 3|. From there onecircuit continues along wire 52 through contacts 5i and 54 to lamp 55 toground. Thus lamp 55 will go on to show that thawing is occurring. Theother circuit continues from bridge point 39' throughtemperature-responsive resistance 29 to ground. Thus current will flowthrough the temperature-responsive element and heat the same. By properdesign, suflicient heat can be generated within the temperature elementto melt the frozen material within chamber I1 and release switch 25 toopen the heating circuit. Any remanent liquid will be flushed out withthe next sample.

In practice, it is possible to freeze a small sample of liquid in a fewseconds. The thawing may be accomplished within a few seconds.Thereafter, the manual switch may be set for a new cycle of temperaturereading.

Various changes may be made in the device. Thus, for example, it may bepossible to provide a flexible diaphragm for the bottom of chamber Iiinstead of plug l2. The flexible diaphragm itself may be utilized tooperate a switch or operate a Bourdon tube to indicate freezing. It isalso possible to have drain pipe 32 extend from the bottom of thechamber in which case a valve may have to be supplied.

What is claimed is:

1. In a device of the character described, a chamber, a Bourdon tubesystem having two ends, one end of said Bourdon tube system terminatingwithin said chamber and. the other end of said Bourdon tube systempassing through said chamber and terminating in a filling portion, gasexpansion means within said chamber but sealed therefrom, said lastnamed means including a gas inlet and a gas outlet so that whencompressed gas is introduced into said inlet a freezing temperaturewithin said chamber will be created, a temperature-responsive resistorwithin said chamber, means connected to said resistor for indicating thetemperature corresponding to the resistance of said resistor, switchmeans in said indicating means circuit, and means conmeeting saidBourdon tube system and said last named switch means for changing theindicating circuit condition when the liquid in said chamber isfreezing, said liquid being adapted to freeze within the chamber andwithin part of the Bourdon tube system passing through said chamber, theinlet for said Bourdon tube system being adapted to receive liquid to betested, said chamber having an outlet for excess liquid so that thedevice may be flushed when a new sample is introduced.

2. The system of claim 1 wherein a source of heating current isprovided, manual switch means for connecting said source to saidresistor and wherein said heating current source includes theBourdon-operated switch, said heating circuit being adapted to be closedonly when liquid in said chamber is frozen.

3. The system according to claim 1 wherein said chamber has an outletnear the top thereof in the normal position of the device, so that aliquid sample may force out dirt and air bubbles ahead of it out throughthe top of the chamber.

4. The system according to claim 1 wherein said gas expansion meansincludes a sleeve, a rod within said sleeve and a coiled capillary tubeWithin said sleeve and around said rod, said capillary tube terminatingwithin said sleeve to discharge gas into a helical space formed betweenthe coils of the capillary within the sleeve and outside of the rod.

5. In a device for determining the freezing point of a liquid, achamber, a pressure responsive system having inlet and outletconnections, one connection opening into said chamber and the otherconnection passing through said chamber and terminating in a fillingportion, said system including a part having a flexible wall portionmovable in response to pressure, means for chilling said chamber and thecontents therein so that liquid to be tested will freeze, a temperatureresponsive resistor disposed in said chamber, circuit means, includingsaid resistor, for indicating the temperature corresponding to theresistance of said resistor, switching means in said circuit, and meansoperated by the movement of said pressure responsive flexible wall foroperating'said switching means, said switching means when operated bysaid pressure responsive wall upon the occurrence of freezing withinsaid chamber disabling said temperature indicating circuit, the inletand outlet connections for said pressure responsive system being shutoff when the liquid in said chamber has frozen and exerting pressureupon the liquid within the pressure responsive system for operating saidswitch, said pressure responsive system being disposed below the normalliquid level in the chamber during normal operation thereof whereby theintroduction of a liquid sample within said device will serve to flushprevious liquid contents therefrom.

6. The construction according to claim 5 wherein said two connections ofthe pressure responsive system extend from the bottom of said chamberand wherein an outlet for the chamber is provided at the top so that anygas bubbles will be eliminated from the system.

7. The system according to claim 5 wherein means are provided forsupplying a heating current to said resistor to thaw the liquid contentsin said chamber after a temperature reading has been obtained.

WILLIAM H. BUSSEY.

Name Date Webber Sept. 29, 1942 Number

